never heard of them, but their website looks good, they might be the real deal... Just contact them and outright ask what their SEO boosting service does and whether they guarantee any results )and what type of results they guarantee).
Personally, if I had a $500 / month budget for SEO I'd bite the bullet and give them a try (but only after they respond to my questions first), if you don't have a SEO budget that's at least $500 per month I wouldn't risk, though as - most likely - their services will be ongoing in order to provide results...